This invention relates to a pattern check device for deciding whether an object pattern being checked is good or bad according to predetermined criteria.
FIG. 1 (a) and (b) illustrate the operation of a conventional pattern check device using a template matching method. In the drawing, the numerals 1 and 1' are object patterns to be checked or tested, and the numerals 2-8 are sampling points respectively indicated with a mark of +.
In FIG. 1 (a) the pattern 1 being checked is a character 8. At this time, the sampling points 2-8 are selected as shown in the drawing by using a template not illustrated to check the existence of a pattern at each point. For example, if a pattern exists, it is a logic 1, and if no pattern, it is a logic 0. Thus, the results of check at each point 2-8 are encoded, and it is recognized which known pattern the pattern checked is classified into by its code.
In FIG. 1 (a), the check results in that a pattern exists (logic 1) at all points of 2-8, which leads to a recognition that the pattern 1 is a character 8. In FIG. 1 (b), only the point 8 has no pattern (logic 0). In this case, an algorithm for deciding whether the pattern is a pattern of a character 0 is previously fixed, and according to the algorithm, it is recognized that it is a character 0.
It is well known that such a pattern check system by template matching has advantages in that only a small quantity of information need be examined due to condensation (the existence of a pattern is detected only at selected sampling points) and the pattern is easily classified by the examined results. Such a pattern check system is effectively used in pattern recognition apparatus such as OCR (Optical Character Reader) where an unknown pattern checked is classified by deciding which standard (known) pattern it corresponds to.
When the template matching method is applied to a pattern check device, some problems are encounted. One is that in checking whether a pattern is good or bad according to whether the pattern exists or not within a window area of an enlarged sampling region, a pattern that is similar but bad is erroneously judged to be good. This is a fatal defect. The reason is as follows. With an alternative decision, i.e. whether a pattern exists or not, if no pattern in the window area, it is judged to be bad. But when a good pattern exists, which is different in size from a good standard pattern, it should not be judged to be bad.
Generally, in the case of a printed pattern, the area of a pattern portion covering a window area varies according to the position checked, and each window area has its characteristic (in this case, large and small sizes of area) at the pattern portion. Therefore, if such a characteristic is not extracted and measured, it is impossible to check the pattern correctly.